1. Field of the Invention
The present invention relates to a system for providing hearing assistance to a user, comprising a microphone arrangement for capturing audio signals, an central signal processing unit for processing the captured audio signals, and means for transmitting the processed audio signals via a wireless audio link to means worn at or in at least one of the user's ears for stimulating the hearing of the user according to the processed audio signals.
2. Description of Related Art
Usually in such systems the wireless audio link is an FM radio link. The benefit of such systems is that sound captured by a remote microphone at the transmission unit can be presented at a high sound pressure level and good signal-to-noise ratio (SNR) to the hearing of the user wearing the receiver unit at his ear(s).
According to one typical application of such wireless audio systems, the stimulating means is a loudspeaker which is part of a receiver unit or is connected thereto. Such systems are particularly helpful for being used in teaching e.g. (a) normal-hearing children suffering from auditory processing disorders (APD), (b) children suffering a unilateral loss (one deteriorated ear), or (c) children with a mild hearing loss, wherein the teacher's voice is captured by the microphone of the transmission unit, and the corresponding audio signals are transmitted to and reproduced by the receiver unit worn by the child, so that the teacher's voice can be heard by the child at an enhanced level, in particular with respect to the background noise level prevailing in the classroom. It is well known that presentation of the teacher's voice at such enhanced level supports the child in listening to the teacher.
According to another typical application of wireless audio systems the receiver unit is connected to or integrated into a hearing instrument, such as a hearing aid. The benefit of such systems is that the microphone of the hearing instrument can be supplemented with or replaced by the remote microphone which produces audio signals which are transmitted wirelessly to the FM receiver and thus to the hearing instrument. FM systems have been standard equipment for children with hearing loss (wearing hearing aids) and deaf children (implanted with a cochlear implant) in educational settings for many years.
Hearing impaired adults are also increasingly using FM systems. They typically use a sophisticated transmitter which can (a) be pointed to the audio-source of interest (during e.g. cocktail parties), (b) put on a table (e.g. in a restaurant or a business meeting), or (c) put around the neck of a partner/speaker and receivers that are connected to or integrated into the hearing aids. Some transmitters even have an integrated Bluetooth module giving the hearing impaired adult the possibility to connect wirelessly with devices such as cell phones, laptops etc.
The merit of wireless audio systems lies in the fact that a microphone placed a few inches from the mouth of a person speaking receives speech at a much higher level than one placed several feet away. This increase in speech level corresponds to an increase in signal-to-noise ratio (SNR) due to the direct wireless connection to the listener's amplification system. The resulting improvements of signal level and SNR in the listener's ear are recognized as the primary benefits of FM radio systems, as hearing-impaired individuals are at a significant disadvantage when processing signals with a poor acoustical SNR.
CA 2 422 449 A2 relates to a communication system comprising an FM receiver for a hearing aid, wherein audio signals may be transmitted from a plurality of transmitters via an analog FM audio link.
Usually the remote wireless microphone of a wireless hearing assistance system is a portable or hand-held device which may be used in multiple environments and conditions: (a) the remote microphone may be held by the hearing-impaired person and pointed towards the desired audio source, such as in a one-to-one conversation to the interlocutor; (b) the remote microphone may be worn around the neck; (c) the remote microphone may be put on a table in a conference or restaurant situation; (d) an external microphone may be connected to the system, which may be worn, for example, in the manner of a lapel microphone or a boom microphone; (e) an external audio source, such as a music player, may be connected to the system.
Usually, the audio signal processing schemes implemented in such wireless systems are a compromise between all wearing modes and operation options. Typically, these signal processing schemes, in particular, the gain model, are fixed, apart from the user's possibility to manually choose between a few beam forming and noise canceling options, which are commonly referred to as different “zoom” positions.
For hearing instruments it is known to perform an analysis of the present acoustic environment (“classifier”) based on the audio signals captured by the internal microphone of the hearing instrument in order to select the most appropriate audio signal processing scheme, in particular with regard to the compression characteristics, for the audio signal processing within the hearing instrument based on the result of the acoustic environment analysis. Examples of classifier approaches are found in US 2002/0090098 A1, US 2007/0140512 A1, EP 1 326 478 A2 and EP 1 691 576 A2.
In EP 1 691 574 A2 and EP 1 819 195 A2 wireless hearing assistance systems are described, comprising a transmission unit including a beam former microphone arrangement and a hearing instrument, wherein a classifier for analyzing the acoustic environment is located in the transmission unit and wherein the result provided by the classifier is used to adjust the gain applied to the audio signals captured by the beam former microphone arrangement in the transmission unit and/or in the receiver unit/hearing instrument.
EP 1 083 769 A1 relates to a hearing aid system comprising a sensor for capturing the movements of the user's body, such as an acceleration sensor, wherein the information provided by such sensor is used in a speech recognition process applied to audio signals captured by the microphone of the hearing aid.
EP 0 567 535 B1 relates to a hearing aid comprising an accelerometer for capturing mechanical vibrations of the hearing aid housing in order to subtract the accelerometer signal from the audio signals captured by the internal microphone of the hearing aid.
WO 2007/082579 A2 relates to a hearing protection system comprising two earplugs, which each comprise a microphone and a loudspeaker connected by wires to a common central audio signal processing unit worn around at the user's body. A detector is provided for detecting whether external audio signals are provided to the central audio signal processing unit from an external communication device connected to the central audio signal processing unit. The output signal of the detector is used to select an audio signal processing mode of the central audio signal processing unit.
US 2004/0136522 A1 relates to a hearing protection system comprising two hearing protection headphones which both comprise an active-noise-reduction unit. The headphones also comprise a loudspeaker for reproducing external audio signals supplied from external communication devices. The system also comprises a boom microphone. A device detector is provided for controlling the supply of power to the boom microphone depending on whether a external communication device is connected to the system.
US 2002/0106094 A1 relates to a hearing aid comprising in internal and a wireless external microphone. A connection detection circuit is provided for activating the power supply of the external microphone once the external microphone is electrically separated from the hearing aid.
It is an object of the invention to provide for a method for providing hearing assistance using a wireless microphone arrangement, wherein the listening comfort, such as the signal to noise ratio (SNR), should be optimized at any time. It is a further object of the invention to provide for a corresponding wireless hearing assistance system.